Reactive Trace Chemicals in Ocean Surface Waters: Hydrogen Peroxide, Manganese and Gallium

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ABSTRACTOCE-0137359Reactive trace species such as Fe have an important effect on surface ocean chemistry and biological productivity. However, other trace species that can influence primary production, affect the chemical distribution of other elements or can be used as tracers have received less attention. For this reason, two PIs from the University of Southern Mississippi will participate in the 4th IOC cruise to the Northwest Pacific to determine Mn, H2O2 and Ga in surface waters, vertical profiles, rain samples, dust dissolution experiments and/or incubation experiments. Determinations of H2O2 will be used for the following: (1) add measurements to a growing dataset aimed at examining photochemical dissolution of dust in surface waters; (2) determine whether it aids in the solubilization of particulate Fe in the surface ocean; and (3) assess rates of photo-production and dark decay. Values for Mn will be compared with Al and Ga to differentiate dust from shelf inputs. In addition, given the longer residence time for Mn in the surface ocean, the PI will attempt to use this metal to provide new insights into Fe inputs to the upper ocean. Comparison of Mn with H2O2 will allow the PIs to determine reductive dissolution of manganese oxides in seawater. Lastly, Ga concentrations will be compared with Al to assess if the former may not be a better proxy for dust inputs to the surface ocean, determine if any fraction is anthropogenic and whether any of the Ga is complexed with organics creating possible Ga-Fe competitive interactions.